# A Novel Mouse Model to Identify Antigen-Specific Immune Responses in Pancreatic Cancer Cachexia

## TL;DR

A new mouse model of pancreatic cancer with cachexia helps study how the condition affects immune responses and could aid in developing better treatments.

## Contribution

A novel orthotopic mouse model of pancreatic cancer cachexia that enables investigation of antigen-specific immune responses.

## Key findings

- The model shows clinically relevant cachexia features like weight loss, fat loss, and muscle wasting.
- Sex differences in cachexia presentation were observed, with males showing more severe skeletal muscle wasting.
- Plasma cytokine differences suggest immune cell functions drive sex bias in cachexia.

## Abstract

Pancreatic Ductal Adenocarcinoma (PDAC) is frequently complicated by cachexia, a serious condition in which patients involuntarily lose body weight due to skeletal muscle wasting and fat loss. Cachexia influences anti-tumor immune responses and hinders therapeutic success in several cancers. However, the mechanisms underlying crosstalk between cachexia and the immune system in PDAC are poorly understood, underscoring an urgent need for further investigations in novel preclinical models. Here, we report a novel orthotopic pancreatic cancer cachexia model in C57BL/6J mice. We conclude that this mouse model recapitulates clinically relevant hallmarks of cachexia, defined by decrease in body weight, fat loss, systemic inflammation and skeletal muscle wasting, thereby providing a robust system for investigating antigen-specific T cell responses in the cachectic background. By elaborating the complex interplay between cachexia and immunomodulation, this model will enable preclinical evaluation of diverse immunotherapies, significantly advancing the search for effective treatment of PDAC patients with cachexia.

Background: Pancreatic Ductal Adenocarcinoma (PDAC) has a dismal five-year survival rate of 13% and is closely associated with cachexia. Cancer cachexia is a multifactorial syndrome characterized by irreversible wasting of skeletal muscles, fat loss and systemic inflammation. While cachexia is known to confer resistance to immune checkpoint inhibition in several cancers, the bidirectional relationship between cachexia and the immune system in PDAC remains unclear, necessitating the development of novel preclinical models. Our laboratory has characterized a novel pancreatic cancer cachexia model in C57BL/6J mice by utilizing the pancreatic cancer cell line called KPCL-4 derived from KPC-LSIY mice (KrasLSL-G12D/+Tp53LSL-R172H/+
Pdx1-Cre/R26LSL-LSIY). Methods: KPCL-4 cells were orthotopically injected into the pancreas of male and female C57BL/6J mice and hallmarks of cachexia were assessed at endpoint by measurement of tumor weight, terminal tumor-adjusted body weight, skeletal muscle, adipose tissue, liver and spleen masses, proteolytic markers and grip strength. Plasma cytokine and chemokine concentrations were quantified by Luminex assay and high-dimensional flow cytometry was used to investigate changes in tumor-infiltrating immune populations. Results: We observed a sex bias in cachexia presentation despite similar tumor weights in male and female mice, whereby males exhibited a >5% decrease in terminal tumor-adjusted body weight (p < 0.001), >50% fat loss (p < 0.001), upregulation of proteolytic markers in skeletal muscles (p < 0.01) and reduction in skeletal muscle mass (p < 0.05), function (p < 0.01) and cross-sectional area (p < 0.0001) whereas females demonstrated conserved skeletal muscle mass with 33% fat loss (p < 0.05), reduction in muscle cross-sectional area (p < 0.0001) and splenomegaly (p < 0.01). While intra-tumoral immune populations did not exhibit sex-specific differences, plasma cytokine concentrations were differentially upregulated in males and females, suggesting functional differences in immune cells as potent drivers of sex bias in KPCL-4-driven cachexia. Conclusions: The KPCL-4 orthotopic PDAC model exhibits prominent hallmarks of cachexia and serves as a novel platform for investigating the complex interplay between cancer cachexia and immunomodulation.